1. Field of the Invention
Methods and apparatuses consistent with the present invention relate to a schottky diode, and more particularly, to a schottky diode having an appropriate low breakdown voltage to be used in a radio frequency identification (RFID) tag and a method for fabricating the same.
2. Description of the Related Art
A radio frequency identification (RFID) system is a non-contact type recognition system which transmits and processes information about products and ambient environmental information by attaching a small-sized chip to all kinds of products. RFID systems can record a greater capacity of information than bar codes. Additionally, recognition of information is possible from a greater distance and several products can be recognized simultaneously. The RFID system includes an RFID tag and a reader. Moreover, the RFID tag includes an RF interface, a control circuit, a memory, and an antenna, which are manufactured in one semiconductor device. The RFID tag is classified as a passive RFID tag and an active RFID tag. A battery is built in the active RFID tag. However, since power is not supplied to the passive RFID tag, the passive RFID tag must operate by an energy supplied from a propagation signal of the reader.
FIG. 1 is a schematic view of a related art passive RFID tag. Referring to FIG. 1, the passive RFID tag includes antennas 10a and 10b for receiving a propagation signal from a reader (not shown), an RF interface and control logic 13 for processing the received signal, and a rectifying unit 11 for rectifying the propagation signal received from the antennas 10a and 10b and for transmitting the rectified signal to the RF interface and control logic 13. In FIG. 1, for explanatory conveniences, the rectifying unit 11 is separated from the RF interface and control logic 13. However, in actuality, the rectifying unit 11 and the RF interface and control logic 13 may be manufactured in a single chip. In this structure, when the propagation signal received from the antennas 10a and 10b has a voltage less than a predetermined level, the propagation signal is applied to the RF interface and control logic 13 via a first schottky diode 11a. However, when the RFID tag is located too close to the reader (not shown) and the intensity of the received propagation signal increases by a predetermined level, a portion of the propagation signal is bypassed via a second schottky diode 11b so that the RF interface and control logic 13 is protected. The voltage in which a bypass occurs is determined by a breakdown voltage of the second schottky diode 11b. 
However, if the breakdown voltage of the second schottky diode 11b is high, a voltage Vaa at both ends of a capacitor 12 may be excessively increased. Then, a voltage to be applied to the RF interface and control logic 13 is increased and malfunction of the RF interface and control logic 13 may occur. Thus, the breakdown voltage of the second schottky diode 11b is preferably as low as possible. However, the breakdown voltage of a schottky diode that is currently used is about −9V and there is a possibility that the voltage Vaa may be increased up to 9V. Accordingly, a voltage that is as low as possible should be applied to the RF interface and control logic 13 by reducing the breakdown voltage of the related art schottky diode to about −3V to −6V.